Improvement in variable cut-off valve-gear for steam-engines



' UNITED STATES HORATIO O. PERRY, 0F BUFFALO, NEW YORK.

IMPROVEMENT IN VARIABLE CUT-OFF VALVE-GEAR FOR STEAM-ENGINES.

Specication forming part of Letters Patent N0. 46,932, dated March 21, 1865A To all whom it may concern Be it known that I, HoRA'rIo O. PERRY, of the city of Buffalo, county of Erie, and State of New York, have invented a certain new and Improved Variable Cut-Off Gear for Steam-Engines; and vI do hereby declare that the following is a full, clear, and exact description of the construction and operation thereof, reference `bein g had to the accompanying drawings, making a part of this specification, in which- Figure I is a side elevation of cut-o gear and section of valve and chest, and Fig. Il is a sectional front elevation of same.

The nature of this invention consists in making the lifting-toes by which the cut-oi' valve is raised in two partsindependent of each other, so that in their movement by the rocking steam-toes one is free to descend while the other is ascending, thus allowing each lifting-toe to remain in constant contact with its steam-toe, so that the valve will be opened instantly after a change of motion ofthe steamtoes, (the steam-toes having a motion coincident with, but slightly leading that of the piston,) and kept open through any required part ofthe ensuing stroke of the piston, or until closed by the operation of an appropriate tripping device; second, in the combination, with the independent lifting-toes, of an adj ustable tripping device, by which the action of the lifting-toes in raising the valve may be broken and the valve allowed to close and the steam be cut oft' at any part of the stroke, (less the lead given the valve).

Letters of like name and kind refer to like parts in each of the figures.

A represents the cut-off valve ot the double-puppet construction operating within the valve-chest B.

C represents the valve-stem, upon which the lifting-toes act to give motion to the valve.

C represents an air-dash pot of ordinary construction, by which the slamming of the valve is prevented.

D represent the steam-toes on the rockshaft D', which is given a motion coincident with but slightly leading that of the' piston by any convenient means.

E represents a lifter-rod divided lon gitudinally into two halves, each half having a lifting-toe formed at its lower end.

The lifter-rod is supported and guided in its movement by the brackets F, bolted to the engine-frame. The two halves of the rod are grooved out, forming a sleeve, through which the valve-stem works.

Motion being given to the rock-shaft and steam-toes D, it is evident that the rising toe will carry with it the corresponding half ofthe lifter, While the other half ofthe lifter Will follow the descending toe.

Each lii'teris provided with a spring-catch, G, which catches under the end of the valve-stem as the lifter rises, thus causing the lifter and valvestem to move together and the valve to open. The catch is thrown out and its hold on the valvestem released and the valve consequently allowed to close, by striking the wedge or cam H, the relative position of which with regard to the motion of the lifter (which is coincident with that of the piston) governs the time the valve is allowed to remain open, and consequently the part of the stroke at which the steam is cut off. By varying this position, which is done by the adj listing-screw I, the point of cutting oft' is varied in a corresponding degree; and since the motion of the rock-shaft and steam-toes is c incident with that of the piston-that is to say, they rockin one direction during the same time that the piston is moving in one direction, and change their motion and rock in the opposite direction, when the piston changes its motion, (except that they are given a slight lead,) it is evident that the rising motion of the lifters will coincide with, or nearly so, the motion of the piston, so that, unless sooner tripped by the cams H the valve will be kept open through the whole stroke of the piston. It will thus be seen that this cut oft' is momentarily adjustable and capable of cutting off at any part ofthe stroke.

The spring-catch G is held out during the downward movements ofthe lifter by a spring bolt, J, which as the lifter completes its downward motion is made to release its hold and allow the catch to spring in again ready to take a new hold of the valve-stem by striking the bracket F or other properly-arranged stop. By this means the catch of the descending lifter is prevented from interfering with the dropping of the valve-stem when the same is tripped at less than full-stroke.

Having thus described said improvements, what I claim as my invention, and desire to secure by Letters Patent, isv l. The combination7 with the rocking steamtoes having a motion coincident7 or nearly so, with the piston, of tWo independent steam lifting-toes actin g upon one valve-stem in such manner that as one ascends the other will descend, by Which construction and the operation of an appropriate adjustable tripping de- -vice the steam may be cut oft' at any required part of the stroke. y

2. In the combination, with the independent steam lifting-toes Ef, of the spring-catches G, and spring-holt J and adjustable tripping-cams H, operating for the purpose and substantiaily as described.

Witnesses: HORATIO 0. PERRY.

B. H. MUEBLE, XV. H. FoRBUsH. 

